var vm = new Vue({
  el: '#app',
  data: {
    math: 90,
    physics: 80,
    english: 20
  },
  computed: {
    sum: function() {
      return this.math + this.physics + this.english;
    },
    average: function() {
      return Math.round(this.sum / 3);
    },
  }
})
